Bogota -- - Griselda Blanco, a convicted drug trafficker who was once known as the "Godmother" and the "Queen of Cocaine," has been shot to death by an unidentified gunman, police in Colombia said Tuesday.

Col. Mauricio Cartagena of Medellin's metropolitan police said Tuesday that the 69-year-old was killed at a butcher shop in the city on Monday.

Cartagena said a man approached Blanco at the shop and fired before escaping on a motorcycle driven by another man. She died on her way to the hospital.

He said the police hadn't identified a firm motive for the killing.

"We don't know why they killed her, but the first hypothesis would be revenge or a settling of accounts," Cartagena said, referring to her past involvement in drug trafficking. Blanco had no charges pending against her in her native Colombia, he added.

Blanco was among the first Colombian women to traffic cocaine to the United States in the 1970s and 1980s. She had been deported back to Colombia in 2004 after serving nearly 20 years behind bars in the United States for drug trafficking and three drug-related killings.

U.S. authorities have described Blanco as a charter member of the "cocaine cowboys" who engaged in drug trafficking, contract killings and gangland shootouts in South Florida in the 1980s. She was known for her love of shopping and beauty salons.